Method for manufacturing double container

Abstract

To provide a method for manufacturing a double container capable of reducing a force required for pulling out an inner bag.SOLUTION: According to the present disclosure, there is provided a method for manufacturing a double-walled container, the method including a step of manufacturing a container body by biaxially stretch blow molding a preform including an inner preform and an outer preform, wherein a first uneven shape is provided on at least one of an outer surface of the inner preform and an inner surface of the outer preform at a portion to be a shoulder portion of the container body after the biaxial stretch blow molding.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a double container. [Background technology]

[0002] Conventionally, double-layered containers having a container body with an outer shell and an inner bag have been known. For example, Patent Document 1 discloses a double-layered container formed by biaxially stretching blow molding an outer shell preform and an inner bag preform in a stacked state. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-10741 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the outer shell and inner bag of such a double container are formed from different materials, or when contents remain inside the inner bag after use, it is desirable to separate the outer shell and inner bag when recycling the double container.

[0005] The outer shell and inner bag can be separated by the user pulling the inner bag from the outer shell, but it has been found that if the inner bag is tightly attached to the outer shell, a large amount of force may be required to pull the inner bag out.

[0006] The present invention has been made in view of the above circumstances, and aims to provide a method for manufacturing a double-layered container that can reduce the force required to pull out the inner bag. [Means for solving the problem]

[0007] According to the present invention, there is provided a method for manufacturing a double container, which includes a step of manufacturing a container body by biaxially stretching blow molding a preform consisting of an inner preform and an outer preform, wherein a first uneven shape is provided on at least one of the outer surface of the inner preform and the inner surface of the outer preform in a region that will become the shoulder of the container body after the biaxially stretching blow molding.

[0008] In the method for manufacturing a double-layered container of the present invention, a first uneven shape that reduces the contact area between the outer surface of the inner preform and the inner surface of the outer preform is provided on at least one of the outer surface of the inner preform and the inner surface of the outer preform in a region that will become the shoulder of the container body. The shoulder is a region where the outer diameter increases with increasing distance from the mouth, so when the inner bag is pulled out of the outer shell, the outer surface of the inner bag is pressed particularly strongly against the inner surface of the outer shell at the shoulder. Therefore, by providing the first uneven shape in the region that will become the shoulder, an uneven shape can be formed in the shoulder when the double-layered container is manufactured, which effectively reduces the force required to pull out the inner bag.

[0009] Various embodiments of the present invention will be described below as examples, and the embodiments shown below can be combined with each other. Preferably, in the above-described method, the first uneven shape is provided on the outer surface of the inner preform. Preferably, in the above-described method, the first uneven shape is not provided on the inner surface of the outer preform. Preferably, in the above-described method, the first uneven shape is formed by transferring an uneven shape formed on a mold by blasting treatment onto the inner preform or the outer preform. Preferably, in the method described above, the double container has a container body having an inner bag and an outer shell, the container body has a mouth, a body, and a bottom, the mouth is a cylindrical portion having an open end, the body is positioned adjacent to the mouth on a side farther from the open end than the mouth and has a larger outer diameter than the mouth, the bottom is configured to close the lower end of the body, the body has a shoulder whose outer diameter increases with increasing distance from the mouth, and at the shoulder of the container body, at least one of the outer surface of the inner bag and the inner surface of the outer shell is provided with a second uneven shape that reduces the contact area between the outer surface of the inner bag and the inner surface of the outer shell, and the outer surface of the inner bag and the inner surface of the outer shell come into contact at the convex parts of the second uneven shape but do not come into contact at the concave parts of the second uneven shape. Preferably, in the method described above, the double container has a container body having an inner bag and an outer shell, the container body has a mouth, a body, and a bottom, the mouth is a cylindrical portion having an open end, the body is positioned adjacent to the mouth on a side farther from the open end than the mouth and has a larger outer diameter than the mouth, the bottom is configured to close the lower end of the body, the body has a shoulder whose outer diameter increases with increasing distance from the mouth, and a second uneven shape is provided on at least one of the outer surface of the inner bag and the inner surface of the outer shell at the shoulder of the container body to reduce the contact area between the outer surface of the inner bag and the inner surface of the outer shell, and the second uneven shape has a shape in which concave and convex portions are irregularly arranged. Preferably, in the above-described method, the second uneven shape is provided on the outer surface of the inner bag. Preferably, in the above-described method, the second uneven shape is not provided on the inner surface of the outer shell. Preferably, in the method described above, the ratio of the depth of the recesses as viewed from the highest part of the convex parts of the second uneven shape to the thickness of the inner bag at the highest part of the convex parts is 0.01 to 0.5. [Brief explanation of the drawings]

[0010] [Figure 1]This is a front view of the double container 1 of the first embodiment of the present invention, showing the state in which the spout attachment member 8 is separated from the container body 2. The dashed dotted line in the figure indicates the boundary where the curvature of the faces that make up the surface shape changes. The same applies to the other figures. [Figure 2] 2A is a cross-sectional view taken along line AA in FIG. 1, FIG. 2B is an end view of cross-section BB in FIG. 2A, FIG. 2C is an enlarged view of region C in FIG. 2B, and FIG. 2D is an end view of cross-section DD in FIG. 2A. [Figure 3] Fig. 3A is an E-E cross-sectional view in Fig. 2A, and Fig. 3B is an exploded view of Fig. 3A. Fig. 3C is a cross-sectional view corresponding to Fig. 3A of a modified example of the first embodiment, and Fig. 3D is an exploded view of Fig. 3C. Fig. 3E is a cross-sectional view corresponding to Fig. 3A of a comparative example, and Fig. 3F is an exploded view of Fig. 3E. [Figure 4] 4A is an enlarged perspective view of the vicinity of the mouth portion 5 in FIG. 1, and FIG. 4B is an enlarged view of region B in FIG. 4A. [Figure 5] FIG. 5A is a perspective view of the mouth-mounted member 8 with a part cut away, and FIG. 5B is a perspective view of the mouth-mounted member 8 as seen obliquely from below. [Figure 6] 6A is a front view of the spout-mounted member 8 mounted on the container body 2, and FIG. 6B is a cross-sectional view taken along line BB in FIG. 6A. [Figure 7] 7A is a cross-sectional view taken along line BB in FIG. 1, FIG. 7B is a front view of the inner bag 4 near the bottom of the container body 2, and FIG. 7C is a cross-sectional view taken along line CC in FIG. 7B. [Figure 8] 8A is a perspective view of the vicinity of the bottom of the container body 2 as seen obliquely from below, and FIG. 8B is a perspective view of the inner bag 4 with the outer shell 3 removed from FIG. 8A. [Figure 9] 9A is a perspective view of the vicinity of the bottom of the container body 2 as seen obliquely from above, and FIG. 9B is a perspective view of the inner bag 4 with the outer shell 3 removed from FIG. 9A. [Figure 10] FIG. 2 is a perspective view showing a state in which the inner preform 14 and the outer preform 13 are separated. [Figure 11]Figure 11A is a front view of the inner preform 14, Figures 11B to 11C are cross-sectional views taken along lines BB and CC in Figure 11A, respectively, Figure 11D is an enlarged view of cross-section DD in Figure 11A, and Figure 11E is a perspective view of the inner preform 14 seen obliquely from above. [Figure 12] Figure 12A is a perspective view showing the state in which the outer preform 13 is being placed on the inner preform 14, Figure 12B is an enlarged view of region B in Figure 12A, Figure 12C is an end view of a cross section passing through the center of the protrusion 14f and the center of the inner preform 14 in Figure 12A, and Figure 12D is an enlarged view of region D in Figure 12C. [Figure 13] FIG. 1 is a perspective view of a preform 15 formed by covering an outer preform 13 on an inner preform 14. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with each other. Furthermore, each feature can be an independent invention.

[0012] 1. First embodiment 1-1. Structure of double container 1 <Basic configuration> As shown in FIG. 1, the double container 1 of the first embodiment of the present invention comprises a container body 2 and a spout attachment member 8.

[0013] As shown in FIG. 1, the container body 2 has a mouth 5, a body 6, and a bottom 7. The mouth 5 is a tubular (preferably cylindrical) portion with an open end 5c. The mouth 5 has an engagement portion 5a to which a mouth attachment member 8, such as a cap or a pump, can be attached. The engagement portion 5a is a male thread portion 5a1 if the mouth attachment member 8 is a screw-type, or a ring-shaped protrusion protruding in the circumferential direction if the mouth attachment member 8 is a stopper-type. The mouth attachment member 8 may have a check valve (not shown). In this case, the contents can be discharged through the mouth attachment member 8, but outside air is prevented from entering the container body 2. The mouth 5 has a flange 5b. The flange 5b can be used to support the mouth 5 when the mouth attachment member 8 is attached to the mouth 5.

[0014] The body 6 is disposed adjacent to the mouth 5 on the side farther from the open end 5c than the mouth 5. The body 6 has a larger outer diameter (in this specification, "outer diameter" means the circumscribed circle diameter if the cross section is not circular) than the mouth 5. The body 6 is cylindrical, and the bottom 7 is provided at the lower end of the body 6 and closes the lower end of the body 6. The body 6 has a shoulder 6b whose outer diameter increases with increasing distance from the mouth 5. The body 6 also has a body main body 6c with a substantially constant outer diameter, located closer to the bottom 7 than the shoulder 6b.

[0015] The diameter of the mouth portion 5 excluding the engaging portion 5a is, for example, 20 to 40 mm, preferably 25 to 35 mm, and specifically, for example, 20, 25, 30, 35, or 40 mm, and may be within a range between any two of the numerical values ​​exemplified here. The length of the mouth portion 5 is, for example, 15 to 35 mm, and specifically, for example, 15, 20, 25, 30, or 35 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0016] As shown in Fig. 2, the container body 2 includes an inner bag 4 and an outer shell 3 arranged to cover the inner bag 4. The inner bag 4 is housed within the outer shell 3 except for a protruding portion 4c, which will be described later. In the following description, the portions of the inner bag 4 that correspond to the mouth 5, body 6, and bottom 7 of the container body 2 will be referred to as the mouth 5, body 6, and bottom 7 of the inner bag 4, respectively. The same applies to the outer shell 3.

[0017] The thickness of the outer shell 3 at the center in the height direction of the container body 2 is, for example, 0.3 to 0.8 mm, preferably 0.4 to 0.5 mm. Specific examples of this thickness include 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 mm, and may be within a range between any two of the values ​​exemplified here. The thickness of the inner bag 4 at the center in the height direction of the container body 2 is, for example, 0.10 to 0.25 mm, preferably 0.15 to 0.20 mm. Specific examples of this thickness include 0.10, 0.15, 0.20, and 0.25 mm, and may be within a range between any two of the values ​​exemplified here.

[0018] If the mouth attachment member 8 is provided with a check valve, the inner bag 4 contracts as the contents of the inner bag 4 are discharged. If the mouth attachment member 8 is not provided with a check valve, the inner bag 4 does not contract even after the contents of the inner bag 4 are discharged, making it difficult to pull out the inner bag 4 through the mouth 5 of the outer shell 3. The present invention facilitates pulling out the inner bag 4 through the mouth 5 of the outer shell by twisting the inner bag 4 to reduce its diameter, so the significance of applying the present invention is particularly evident when the mouth attachment member 8 is not provided with a check valve. However, even if the mouth attachment member 8 is provided with a check valve, the diameter of the inner bag 4 may not appropriately reduce when it contracts, so the significance of applying the present invention is also evident when the mouth attachment member 8 is provided with a check valve.

[0019] An outside air inlet hole 16 is provided in the body 6 or the bottom 7. The outside air inlet hole 16 is a through-hole that penetrates the outer shell 3, and outside air can be introduced into the intermediate space between the outer shell 3 and the inner bag 4 through the outside air inlet hole 16. When the double container 1 is a so-called squeeze-type container that ejects the contents by compressing the outer shell 3, it is preferable to provide a check valve that controls the flow of air in and out through the outside air inlet hole 16. The check valve is preferably configured to close the outside air inlet hole 16 when the outer shell 3 is compressed and to open the outside air inlet hole 16 when the compressive force is released. In this case, when a compressive force is applied to the outer shell 3, the compressive force is more easily applied to the inner bag 4, and after the contents are ejected, outside air is quickly introduced into the intermediate space, allowing the outer shell 3 to quickly restore its shape.

[0020] When a check valve is provided in the outside air introduction hole 16, it is preferable that the outside air introduction hole 16 be disposed in a recess 6d provided in the body 6. In this case, it is possible to prevent the check valve from interfering with the shrink film when the body 6 is covered with the shrink film. It is also preferable to provide a groove 6e extending from the recess 6d toward the mouth 5. The groove 6e extends to a position that is not covered with the shrink film. This prevents the recess 6d from being sealed with the shrink film.

[0021] <Uneven shape 9 on the inner surface of the mouth 5> As shown in FIG. 2, the inner surface of at least one of the mouth 5 and a position of the body 6 adjacent to the mouth 5 is preferably provided with an uneven pattern 9 in which grooves 9a and protrusions 9b alternate in the circumferential direction of the mouth 5. The uneven pattern 9 is provided on the inner surface of the inner bag 4. The number of grooves 9a is, for example, 4 to 30, and preferably 10 to 20. The grooves 9a and protrusions 9b preferably extend non-parallel to the circumferential direction of the mouth 5. The extending direction of the grooves 9a and protrusions 9b is preferably 0 to 60 degrees, and preferably 0 to 30 degrees, relative to the axial direction of the mouth 5. Specific examples of this angle are 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 degrees, and may be within a range between any two of the values ​​exemplified here. The uneven shape 9 may be provided only in the mouth 5 or may be provided in a position on the body 6 adjacent to the mouth 5, but is preferably provided across the mouth 5 and body 6. The uneven shape 9 may be formed by reducing the thickness of the recesses 9a or by increasing the thickness of the protrusions 9b compared to other parts of the mouth 5 of the inner bag 4, or by reducing the thickness of the recesses 9a and increasing the thickness of the protrusions 9b.

[0022] Because the thickness of the ridges 9b is greater than the thickness of the recesses 9a, when the twist applied by the mouth 5 is transmitted to the body 6, the force is transmitted more easily to the ridges 9b than to the recesses 9a, and the ridges 9b rotate faster than the recesses 9a, resulting in the formation of creases in the inner bag 4 along the recesses 9a and their extensions, making it easier for the inner bag 4 to fold into pleats. For this reason, providing the uneven surface 9 causes the body 6 to fold into pleats, thereby quickly reducing the diameter of the body 6. It is preferable not to provide an uneven surface on the outer surface of the inner bag 4. This is because if an uneven surface is provided on the outer surface of the inner bag 4, the inner bag 4 and the outer shell 3 will engage with each other in the rotational direction of the inner bag 4, making it more difficult for the inner bag 4 to rotate relative to the outer shell 3.

[0023] If the thickness of the inner bag 4 at the ridges 9b of the mouth 5 (the radius of the circumscribing circle of the inner bag 4 minus the radius of the inscribed circle passing through the apexes of the ridges 9b) is T and the depth of the recesses 9a (the radius of the inscribed circle passing through the bottoms of the recesses 9a minus the radius of the inscribed circle passing through the apexes of the ridges 9b) is D, the maximum value of D / T is, for example, 0.2 to 0.8, and preferably 0.3 to 0.5. Specific examples of this value are 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8, and may be within a range between any two of the values ​​exemplified here. The thickness of the inner bag 4 at the mouth 5 other than the concave-convex shape 9 is, for example, 1 to 2 mm, specifically, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0 mm, or may be within a range between any two of the numerical values ​​exemplified here. The depth of the concave streaks 9a at the portion where the depth is greatest is, for example, 0.3 to 1.0 mm, specifically, for example, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 mm, or may be within a range between any two of the numerical values ​​exemplified here.

[0024] The distance from the opening edge 5c of the mouth portion 5 to the upper end of the uneven shape 9 is, for example, 0 to 30 mm, specifically, for example, 0, 5, 10, 15, 20, 25, or 30 mm, and may be within a range between any two of the numerical values ​​exemplified here. The distance from the upper end to the lower end of the uneven shape 9 is, for example, 10 to 40 mm, specifically, for example, 10, 15, 20, 25, 30, 35, or 40 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0025] <Structure of bottom 7> As shown in Figures 7 to 9, a protrusion 4e is provided on the bottom 7 of the inner bag 4. An annular protrusion 3b is provided on the bottom 7 of the outer shell 3, and a through-hole 3c is provided in the area inside the annular protrusion 3b. The protrusion 4e is inserted into the through-hole 3c, thereby positioning the inner bag 4 with respect to the outer shell 3. The annular protrusion 3b and its area inside are hardly stretched during biaxial stretch blow molding, so both the outer shell 3 and the inner bag 4 have a large wall thickness.

[0026] If the outer diameter of the annular protrusion 3b is D1 and the inner diameter of the mouth portion 5 of the outer shell 3 is D2, then D1 / D2 is preferably 0.9 or less. Since the thickness of the inner bag 4 is greater at the annular protrusion 3b and the region inside it, the smaller D1 / D2 is, the more easily the diameter of the bottom portion 7 of the inner bag 4 is reduced. D1 / D2 is, for example, 0.1 to 0.9, and specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, and may be within a range between any two of the numerical values ​​exemplified here.

[0027] The bottom 7 of the container body 2 (i.e., the bottoms 7 of the inner bag 4 and the outer shell 3) is provided with a bottom recessed region 7a and a peripheral region 7b surrounding the bottom recessed region 7a. The bottom recessed region 7a is a region of the bottom 7 recessed toward the inside of the container body 2. The peripheral region 7b serves as the contact surface of the container body 2. As shown in FIG. 7A, the thickness of the inner bag 4 and the outer shell 3 gradually decreases along the peripheral surface 7a1 of the bottom recessed region 7a as it approaches the peripheral region 7b. The peripheral surface 7a1 is an inclined surface that slopes away from the center of the bottom 7 toward the peripheral region 7b. In other words, the peripheral surface 7a1 forms part of a cone that tapers toward the bottom surface 7a2 of the bottom recessed region 7a. The bottom surface 7a2 of the bottom recessed region 7a is generally flat. Therefore, the bottom recessed region 7a has a generally truncated cone shape.

[0028] The bottom surface 7a2 of the bottom recessed region 7a is difficult to stretch during biaxial stretch blow molding and is therefore likely to have a large wall thickness. Therefore, the smaller the diameter D3 of the bottom surface 7a2 (in other words, the diameter of the region surrounded by the boundary between the bottom surface 7a2 and the peripheral surface 7a1), the easier it is for the bottom 7 of the inner bag 4 to be reduced in diameter. D3 / D2 is preferably 0.9 or less. D3 / D2 is, for example, 0.1 to 0.9, specifically, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or 0.9, and may be within a range between any two of the values ​​exemplified here.

[0029] <Alternating thickness shape 10 provided on bottom 7> 7 to 9, it is preferable that the bottom 7 of the inner bag 4 has an alternating thickness shape 10 in which thin portions 10a and thick portions 10b that are thicker than the thin portions 10a appear alternately in the circumferential direction of the inner bag 4. By providing the bottom 7 with the alternating thickness shape 10, when the inner bag 4 is twisted, the thin portions 10a bend, causing the bottom 7 to deform like an accordion, making it easier for the diameter of the bottom 7 to be reduced.

[0030] As shown in FIG. 7C , the peripheral surface 7a1 is thicker than the side surface 4d of the inner bag 4 near the bottom 7. Therefore, providing the alternating thickness shape 10 on the peripheral surface 7a1 is particularly important for facilitating the diameter contraction of the bottom 7. Furthermore, the peripheral region 7b is less likely to deform than the side surface 4d of the inner bag 4 near the bottom 7. Therefore, providing the alternating thickness shape 10 on the peripheral region 7b is particularly important. Therefore, it is preferable to provide the alternating thickness shape 10 on at least one of the peripheral surface 7a1 and the peripheral region 7b of the bottom recessed region 7a, and it is even more preferable to provide the alternating thickness shape 10 so that it straddles the peripheral surface 7a1 and the peripheral region 7b. It is also preferable to provide the alternating thickness shape 10 so that it straddles the peripheral region 7b and the side surface 4d of the inner bag 4. Providing the alternating thickness shape 10 in this manner makes the bottom 7 even easier to contract.

[0031] 8B, the thin portions 10a and the thick portions 10b are preferably provided so as to extend radially from the center of the bottom portion 7. The number of thin portions 10a is, for example, 4 to 30, and preferably 10 to 20.

[0032] The thin-walled portion 10a can be formed by providing grooves 11 on one or both of the inner and outer surfaces of the inner bag 4. The grooves 11 on the inner surface of the inner bag 4 and the grooves 11 on the outer surface face each other. The area between two adjacent grooves 11 becomes the thick-walled portion 10b.

[0033] In a cross section perpendicular to the height direction of the inner bag 4 (such as the cross section in FIG. 7C ), if the thickness of the inner bag 4 at the thin-walled portion 10a is T1 and the thickness of the inner bag 4 at the thick-walled portion 10b is T2, the minimum value of T1 / T2 is preferably 0.8 or less. The minimum value of T1 / T2 is the minimum value when T1 / T2 is calculated at each height position by moving the cross section along the height direction of the inner bag 4. The smaller the T1 / T2 ratio, the thinner the thin-walled portion 10a is compared to the thick-walled portion 10b, making the bottom portion 7 more likely to deform like an accordion. This value is preferably 0.1 or greater. If this value is too small, the thickness at the thin-walled portion 10a will be too small, making pinholes more likely to occur. This value is, for example, 0.1 to 0.8, specifically, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, and may be within a range between any two of the values ​​exemplified here.

[0034] <Engagement Structure Between Mouth-Attachment Member 8 and Inner Bag 4, and Engagement Structure Between Inner Bag 4 and Mouth 5 of Outer Shell 3> The mouth attachment member 8 is preferably configured to be attachable to the mouth 5, and configured so that the inner bag 4 rotates as the mouth attachment member 8 rotates (here, relative rotation with respect to the outer shell 3). With this configuration, it is possible to twist the inner bag 4 by rotating the mouth attachment member 8. Because the body 6 of the container body 2 has a larger outer diameter than the mouth 5, it is not easy to pull the inner bag 4 through the mouth 5 of the outer shell 3 simply by pulling the inner bag 4. However, by twisting the inner bag 4 and reducing the diameter of the body 6 of the inner bag 4, the body 6 of the inner bag 4 can more easily pass through the mouth 5 of the outer shell 3, and the inner bag 4 can be easily pulled out of the outer shell 3.

[0035] The engagement structure between the mouth-attached member 8 and the inner bag 4 will now be described in more detail.

[0036] 2 and 4, the inner bag 4 has a protruding portion 4c that protrudes from the open end 3a of the outer shell 3. The protruding portion 4c has a protruding tube 4c1, an engaging protrusion 4c2, an engaging flange 4c3, and an abutting flange 4c4.

[0037] The engaging protrusion 4c2 protrudes radially outward from the circumferential surface of the protruding tube 4c1. The engaging flange 4c3 is an annular portion located farther from the open end 3a than the engaging protrusion 4c2 and having a larger diameter than the protruding tube 4c1. The abutting flange 4c4 is an annular portion located at a position abutting the open end 3a and having a larger diameter than the protruding tube 4c1. The abutting flange 4c4 abuts against the open end 3a, thereby preventing the inner bag 4 from falling into the outer shell 3. Alternatively, the abutting flange 4c4 may be omitted and the engaging protrusion 4c2 may be abutted against the open end 3a to prevent the inner bag 4 from falling into the outer shell 3.

[0038] As shown in FIGS. 4 to 6, the mouth attachment member 8 includes an outer tube 8a, a middle tube 8b, an inner tube 8c, an engagement portion 8d, a claw portion 8e, a top plate 8f, and a nozzle 8g.

[0039] An engagement portion 8d is provided on the inner surface of the outer cylinder 8a. The engagement portion 8d is an engagement portion that engages with the engagement portion 5a of the mouth portion 5, and the mouth-mounted member 8 is attached to the mouth portion 5 by engaging the engagement portion 8d with the engagement portion 5a.

[0040] The intermediate cylinder 8b has a smaller diameter than the outer cylinder 8a and is disposed above the outer cylinder 8a. The inner cylinder 8c has a smaller diameter than the intermediate cylinder 8b and is a so-called inner ring that is disposed inside the outer cylinder 8a and the intermediate cylinder 8b. The upper surface of the intermediate cylinder 8b is covered with a top plate 8f. A nozzle 8g is provided on the top plate 8f.

[0041] Claws 8e are provided on the inner surface of the intermediate cylinder 8b. A plurality of claws 8e (eight in this embodiment) are provided and spaced apart in the circumferential direction. The number of claws 8e is, for example, 1 to 20, and preferably 4 to 12. Each claw 8e has an upper surface 8e1 and a lower inclined surface 8e2. A through hole 8h is provided in the top plate 8f at a position facing the claw 8e.

[0042] The mouth attachment member 8 having such a shape can be manufactured using a split mold that opens and closes in the vertical direction. Because the through-hole 8h and the upper surface 8e1 can be formed using the protrusions on the upper mold, the claws 8e can be formed without forcibly removing the lower mold. Therefore, it is not necessary to set the protrusion amount of the claws 8e to an amount that allows for forcible removal, and the protrusion amount can be set to an amount suitable for engagement with the inner bag 4 (e.g., 1 mm or more).

[0043] In this embodiment, the engaging portion 5a is a male threaded portion 5a1, and the engaging portion 8d is a female threaded portion 8d1 that can be threaded onto the male threaded portion 5a1. Therefore, the mouth attachment member 8 can be attached to the mouth 5 by rotating the mouth attachment member 8 relative to the mouth 5 in the tightening direction (usually clockwise when viewed from above) (hereinafter, relative rotation with respect to the mouth 5 will also be simply referred to as "rotation"). When the mouth attachment member 8 is rotated in the tightening direction, the female threaded portion 8d1 is threaded onto the male threaded portion 5a1 while the outer peripheral surface of the inner tube 8c shown in FIG. 5B comes into close contact with the inner peripheral surface of the inner bag 4. At this time, friction between the outer peripheral surface of the inner tube 8c and the inner peripheral surface of the inner bag 4 causes the mouth 5 of the inner bag 4 to rotate together with the mouth attachment member 8, resulting in a twisting of the inner bag 4. Before the mouth-attaching member 8 is attached, the inner bag 4 is filled with contents, and if the inner bag 4 is twisted, the contents inside the inner bag 4 will spill out. To prevent this problem from occurring, the inner bag 4 and the outer shell 3 can be tightly fitted together at the mouth 5 to prevent the inner bag 4 from rotating relative to the outer shell 3. However, simply fitting them tightly together creates a new problem in that it becomes difficult to pull the inner bag 4 out of the outer shell 3.

[0044] Therefore, in this embodiment, a configuration is adopted in which the first resistance to relative rotation of the inner bag 4 in one direction relative to the outer shell 3 at the mouth 5 is greater than the second resistance to relative rotation in the other direction. For example, if the male thread portion 5a1 is a right-handed thread, the one direction and the other direction are the clockwise and counterclockwise directions, respectively, when viewed from above the container body 2. In other words, the one direction is the direction in which the mouth attachment member 8 is tightened, and the other direction is the direction in which the mouth attachment member 8 is loosened. With this configuration, the inner bag 4 is less likely to rotate relative to the outer shell 3 when attaching the mouth attachment member 8, thereby preventing the inner bag 4 from twisting when attaching the mouth attachment member 8. Furthermore, because the second resistance to relative rotation in the other direction is relatively small, when separating the inner bag 4 from the outer shell 3 after use, the inner bag 4 can be easily twisted and reduced in diameter by rotating the mouth 5 of the inner bag 4 relative to the outer shell 3 in the other direction, making it easy to pull the inner bag 4 out of the outer shell 3.

[0045] Specifically, the inner bag 4 and the outer shell 3 are engaged with each other at the opening 5, and this engagement is configured so that the first resistance is greater than the second resistance. More specifically, as shown in FIGS. 2C and 4B, the engagement is between a protrusion 4f provided on the outer peripheral surface of the inner bag 4 and a recess 3f provided on the inner peripheral surface of the outer shell 3. As shown in FIG. 2C, a tapered surface 4f1 is provided on the right side (loosening direction side) of the protrusion 4f to reduce the second resistance. On the other hand, no tapered surface is provided on the left side (tightening direction side) of the protrusion 4f. Therefore, at the opening 5, the resistance to rotating the inner bag 4 relative to the outer shell 3 in the tightening direction (first resistance) is greater than the resistance to rotating the inner bag 4 relative to the outer shell 3 in the loosening direction (second resistance). In this embodiment, two pairs of protrusions 4f and recesses 3f are provided at 180-degree intervals, but the number of pairs of protrusions 4f and recesses 3f may be one or three or more.

[0046] The second resistance may be reduced by providing a tapered surface in the recess 3f instead of or in addition to providing the tapered surface 4f1. Furthermore, the recess-recess engagement may be an engagement between a recess provided on the outer peripheral surface of the inner bag 4 and a protrusion provided on the inner peripheral surface of the outer shell 3. Furthermore, although the recess 3f is configured as a through-hole that penetrates the outer shell 3, it is sufficient that the recess 3f can engage with the protrusion 4f, and it is not necessary for the recess 3f to penetrate the outer shell 3.

[0047] As the mouth-mounting member 8 is further rotated in the tightening direction, the female thread portion 8d1 threads into the male thread portion 5a1, and the claw portion 8e gradually approaches the protruding portion 4c. At a certain point, the lower inclined surface 8e2 abuts against the engaging flange 4c3. If the mouth-mounting member 8 is further rotated in the tightening direction, the claw portion 8e overcomes the engaging flange 4c3, resulting in the state shown in FIG. 6. In this state, the claw portion 8e is positioned between the engaging flange 4c3 and the abutting flange 4c4. The engaging flange 4c3 is accommodated in the gap between the claw portion 8e and the top plate 8f. As shown in FIG. 6B, the protruding tube 4c1 is positioned between the claw portion 8e and the inner tube 8c. If the male thread portion 5a1 and the female thread portion 8d1 are not fully tightened at this point, the claw portion 8e will overcome the engaging protrusion 4c2, guided by the circumferential inclined surface 4c5 on the engaging protrusion 4c2, allowing the mouth-mounting member 8 to further rotate in the tightening direction. After the male screw portion 5a1 and the female screw portion 8d1 are fully tightened, the mouth portion attachment member 8 cannot rotate in the tightening direction and cannot move in the axial direction of the mouth portion 5.

[0048] In this state, the engaging protrusion 4c2 engages with the claw portion 8e of the mouth attachment member 8 in the rotational direction of the mouth attachment member 8, and the engaging flange 4c3 engages with the claw portion 8e of the mouth attachment member 8 in the axial direction of the mouth 5. In other words, the claw portion 8e engages with the engaging protrusion 4c2 and the engaging flange 4c3.

[0049] Therefore, when the mouth-attaching member 8 is rotated in the loosening direction (usually counterclockwise when viewed from above) after the contents inside the inner bag 4 have been used up, the inner bag 4 rotates in conjunction with the rotation of the mouth-attaching member 8. This causes the inner bag 4 to twist and reduce in diameter.

[0050] When the mouth attachment member 8 is further rotated in the loosening direction to release the engagement between the female thread portion 8d1 and the male thread portion 5a1, the mouth attachment member 8 becomes movable in a direction away from the open end 3a (i.e., in the axial direction of the mouth 5). Because the engagement flange 4c3 is engaged with the mouth attachment member 8 in the axial direction of the mouth 5, when the mouth attachment member 8 is moved in the axial direction of the mouth 5, the inner bag 4 also moves together with the mouth attachment member 8, and the inner bag 4 is pulled out of the outer shell 3.

[0051] As described above, according to the configuration of this embodiment, by simply rotating the mouth attachment member 8 in the loosening direction, the inner bag 4 is twisted and reduced in diameter, and then pulled out from the outer shell 3, making it possible to smoothly separate the inner bag 4 and the outer shell 3 with a simple operation.

[0052] <Uneven shape on the outer surface of the inner bag 4 or the inner surface of the outer shell at the shoulder portion 6b> Since shoulder 6b is a region whose outer diameter increases with increasing distance from mouth 5, when inner bag 4 is pulled out of outer shell 3, the outer surface of inner bag 4 is pressed particularly strongly against the inner surface of outer shell 3 at shoulder 6b. Therefore, by reducing the frictional resistance between inner bag 4 and outer shell 3 at shoulder 6b, the force required to pull out inner bag 4 can be effectively reduced. Therefore, in this embodiment, as shown in Figures 3A and 3B, shoulder 6b of container body 2 has an uneven shape 35 on at least one of the outer surface of inner bag 4 and the inner surface of outer shell 3, which reduces the contact area between the outer surface of inner bag 4 and the inner surface of outer shell 3.

[0053] The unevenness 35 may be provided only on the outer surface of the inner bag 4, only on the inner surface of the outer shell 3, or on both the outer surface of the inner bag 4 and the inner surface of the outer shell 3. In this embodiment, as shown in FIGS. 3A and 3B, the unevenness 34 is provided on the outer surface of the inner bag 4, and the unevenness is not provided on the inner surface of the outer shell 3. In this case, the outer surface of the inner bag 4 and the inner surface of the outer shell 3 come into contact at the convex portions 34a of the unevenness 34 but not at the concave portions 34b, thereby reducing the contact area. As shown in a modified example in FIGS. 3C and 3D, the inner surface of the outer shell 3 may be provided with an unevenness 33 that is not complementary to the unevenness 34. In this case, the contact area between the outer surface of the inner bag 4 and the inner surface of the outer shell 3 is also reduced.

[0054] 3E to 3F , when complementary uneven shapes 34, 33 are provided on the outer surface of inner bag 4 and the inner surface of outer shell 3, the convex portions 34a of uneven shape 34 of inner bag 4 fit into the concave portions 33b of uneven shape 33 of outer shell 3, and the concave portions 34b of uneven shape 34 of inner bag 4 fit into the convex portions 33a of uneven shape 33 of outer shell 3, thereby increasing the contact area between the outer surface of inner bag 4 and the inner surface of outer shell 3. This type of uneven shape is not an "uneven shape 35 that reduces the contact area between the outer surface of inner bag 4 and the inner surface of outer shell 3."

[0055] The ratio of the depth of recesses 34b as seen from the highest portions to the thickness of inner bag 4 at the highest portions of protrusions 34a of uneven shape 34 is, for example, 0.01 to 0.5, and more specifically, for example, 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, or 0.5, and may be within a range between any two of the values ​​exemplified here. If this ratio is too small, the effect of reducing frictional resistance may be insufficient, and if it is too large, pinholes may be more likely to form in inner bag 4.

[0056] The uneven shape 35 may be a shape in which convex and concave portions are arranged regularly or irregularly. The inner bag 4 having an uneven shape 34 on its outer surface can be formed by biaxially stretching blow molding an inner preform 14 having an uneven shape on its outer surface. The outer shell 3 having an uneven shape 33 on its inner surface can be formed by biaxially stretching blow molding an outer preform 13 having an uneven shape on its inner surface.

[0057] The uneven shape 35 may be formed in a region including the shoulder portion 6b, but is preferably formed in a region including the shoulder portion 6b and the bottom portion 7. This is because the frictional resistance between the outer surface of the inner bag 4 and the inner surface of the outer shell 3 is likely to be large also in the bottom portion 7.

[0058] <Laser marking> Possible methods for handling the separated inner bag 4 include horizontal recycling, cascade recycling, and thermal recycling. However, if the inner bag 4 does not have any markings, it is difficult for the user to determine how to handle the separated inner bag 4. For containers in which the outer shell 3 and inner bag 4 are not separated, it is easy to stamp a recycling mark on the container by providing a mold for molding with a predetermined recycling mark shape. On the other hand, when the outer shell 3 and inner bag 4 are separated, as in this embodiment, a recycling mark different from that on the outer shell 3 must be provided on the inner bag 4. However, it is impossible to stamp a recycling mark only on the inner bag 4 using a mold for molding. While it is also possible to provide a recycling mark on the inner preform 14 (described below), it is difficult to accurately control the extent to which portions of the inner preform 14 are stretched during biaxial stretch blow molding of the inner preform 14. Furthermore, the recycling mark is also stretched during stretching of the inner preform 14, making it difficult to clearly mark a recycling mark only on the inner bag 4.

[0059] In this embodiment, as shown in FIG. 1, an information transmission mark 22 is printed on the inner bag 4 by irradiation with laser light. Printing by laser light irradiation is performed by altering the target object (oxidizing, peeling, coloring, discoloration, etc.) with the laser light. The laser light irradiation can be performed using a laser marker. A laser marker is a device that can irradiate by scanning laser light in at least two dimensions, and is a device that can print a predetermined shape by moving the spot of laser light along a predetermined path. The laser marker used to print on the inner bag 4 is preferably a fiber laser marker.

[0060] Since printing on the inner bag 4 is performed through the outer shell 3, it is preferable that the laser light has a wavelength that is not easily absorbed by the outer shell 3. The wavelength of the laser light is preferably 500 to 1150 nm, preferably 950 to 1150 nm, preferably 1000 to 1100 nm, and more preferably 1064 nm. Specific examples of this wavelength include 500, 950, 1000, 1010, 1020, 1030, 1040, 1050, 1060, 1064, 1070, 1080, 1090, 1100, and 1150 nm, and may be within a range between any two of the values ​​exemplified here. Because this laser light is not easily absorbed by PET, when the outer shell 3 is made of PET, it can pass through the outer shell 3 and print on the inner bag 4.

[0061] However, because this laser light is also poorly absorbed by polyolefins (e.g., polypropylene and polyethylene), it is preferable to incorporate a laser marking agent into the inner bag 4. The laser marking agent is a substance that absorbs laser light more easily than the resin that constitutes the inner bag 4 and / or is more likely to discolor due to absorption of laser light than the resin that constitutes the inner bag 4. By incorporating a laser marking agent into the inner bag 4, it becomes easier to print on the inner bag 4. Specific examples of preferred laser marking agents include antimony-doped tin oxide, antimony or a compound thereof, an association-type basic dye precursor (2,2-bis{4-[6'-(cyclohexyl-N-methylamino)-3'-methylspiro[phthalido-3,9'-xanthene]-2'-ylamino]phenyl}propane), a phthalide dye precursor, a fluoran dye precursor, a spiropyran dye precursor, and a lactam dye precursor. The laser marking agent is preferably in a form suitable for molding, such as pellets, particles, or paste, as a masterbatch (a resin material containing the laser marking agent at a predetermined concentration).

[0062] The information transmission mark 22 is a mark for transmitting information regarding how to handle the inner bag 4, and may be composed of only a design, only text, or a combination of both. In one example, the information transmission mark 22 is composed of a recycling mark 22a and a message 22b. In the example of FIG. 1, the recycling mark 22a indicates that the inner bag 4 is made of general plastic, and the message 22b indicates that the recommended recycling method is thermal recycling. Because the information transmission mark 22 is printed on the inner bag 4, it remains attached to the inner bag 4 even after the inner bag 4 is separated from the outer shell 3. This makes it easy for users to determine how to handle the inner bag 4.

[0063] It is preferable to provide a gap (air layer) between the inner bag 4 and the outer shell 3 at the location where the information transmission indicia 22 is printed. If there is a gap, smoke will be generated when printing the information transmission indicia 22, and fine particles contained in the smoke will adhere to the inner surface of the outer shell 3 or the outer surface of the inner bag 4. These fine particles act as a lubricant, reducing the resistance when the inner bag 4 is pulled out of the outer shell 3.

[0064] It is preferable that the information transmission mark 22 be printed only on the inner bag 4, but depending on the irradiation conditions of the laser light, it may also be printed on the outer shell 3. In this case, it is preferable that the information transmission mark 22 printed on the outer shell 3 is thinner (less visible) than the information transmission mark 22 printed on the inner bag 4. It is also preferable that the outer shell 3 does not have any uneven shapes due to the printing of the information transmission mark 22, and that the surface of the outer shell 3 is smooth.

[0065] The outer shell 3 is provided with an information transmission marking 23. The information transmission marking 23 is a mark for transmitting information regarding how to handle the outer shell 3, and may be composed of only a design, only text, or a combination of both. In the example shown in FIG. 1, the information transmission marking 23 is composed of a recycling marking 23a and a message 23b. In the example shown in FIG. 1, the recycling marking 23a indicates that the outer shell 3 is made of PET, and the message 23b indicates that horizontal recycling is the recommended recycling method. The method for attaching the information transmission marking 23 is not particularly limited, but because methods such as attaching a sticker or printing with ink have a negative impact on the recyclability of the outer shell 3, it is preferable to attach the information transmission marking 23 by printing using laser light.

[0066] When the outer shell 3 is made of PET, the wavelength of the laser light is preferably 8.0 to 12 μm, and more preferably 9.0 to 11 μm. Specific examples of this wavelength include 8.0, 8.5, 9.0, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9, 11.0, 11.5, and 12.0 μm, and may be within a range between any two of the values ​​exemplified here. Laser light of such wavelengths is easily absorbed by the outer shell 3, and is therefore suitable for printing the information transmission marking 23 on the outer shell 3. The laser marker used to print on the outer shell 3 is preferably a CO2 laser marker capable of emitting laser light of the above wavelengths.

[0067] It is preferable that the information transmission mark 23 is printed only on the outer shell 3, but depending on the irradiation conditions of the laser light, it may also be printed on the inner bag 4. In this case, it is preferable that the information transmission mark 23 printed on the inner bag 4 is thinner (has lower visibility) than the information transmission mark 23 printed on the outer shell 3. It is preferable that the information transmission mark 23 is provided so as not to overlap with the information transmission mark 22.

[0068] Additionally, the outer shell 3 may be provided with a covering region that obscures the information transmission indicator 22. While there are no particular limitations on the method for providing the covering region, methods such as attaching a sticker or printing with ink have a negative impact on the recyclability of the outer shell 3, and therefore the covering region is preferably provided by printing using laser light. In this case, the information transmission indicator 22 can be seen only after the inner bag 4 is pulled out, thereby preventing user confusion that would otherwise occur if both the information transmission indicator 22 and the information transmission indicator 23 were visible on the container body 2 before the inner bag 4 was pulled out. Furthermore, if the information transmission indicator 22 is a display with a creative element, such as a lottery or fortune telling, providing the covering region can provide an incentive to pull out the inner bag 4.

[0069] 1-2. Manufacturing method of double container 1 As shown in Figures 10 to 13, the container body 2 can be formed by heating and biaxially stretching blow molding a preform 15 formed by covering an inner preform 14 that will become the inner bag 4 with an outer preform 13 that will become the outer shell 3.

[0070] <Configuration of inner preform 14, outer preform 13, and preform 15> As shown in Figure 10, the inner preform 14 is cylindrical with a bottom and includes a mouth portion 14a, a body portion 14b, and a bottom portion 14c. A protrusion 14d is provided at the open end of the mouth portion 14a. The protrusion 14d does not deform during molding and remains in its original shape to become the protrusion 4c. Therefore, the matters described for the protrusion 4c also apply to the protrusion 14d. The bottom portion 14c is provided so as to close the lower end of the body portion 14b. A positioning pin 14c1 is provided on the bottom portion 14c.

[0071] 11, an uneven shape 19 is provided on the inner surface of the inner preform 14. The uneven shape 19 remains as it is or is stretched during molding to become the uneven shape 9 of the container body 2. The explanation regarding the uneven shape 9 also applies to the uneven shape 19 as long as it is not contrary to the spirit thereof.

[0072] As shown in Figures 10 and 11, an alternating thickness shape 20 is provided near the bottom 14c of the inner preform 14, in which thin sections 20a and thick sections 20b that are thicker than the thin sections 20a alternate in the circumferential direction. The alternating thickness shape 20 is stretched during biaxial stretch blow molding to form the alternating thickness shape 10. The number of thin sections 20a is, for example, 4 to 30, and preferably 10 to 20. The thin sections 20a are preferably provided in the longitudinal direction of the inner preform 14.

[0073] The thin-walled portion 20a can be formed by providing grooves 21 on one or both of the inner and outer surfaces of the inner preform 14. If grooves 21 are provided on the inner surface of the inner preform 14, grooves 11 will be formed on the inner surface of the inner bag 4 after molding. If grooves 21 are provided on the outer surface of the inner preform 14, grooves 11 will be formed on the outer surface of the inner bag 4 after molding, and grooves 11 will also be formed on the inner surface of the inner bag 4 at positions opposite the grooves 11 on the outer surface. This is because the resin at positions opposite the grooves 11 is pressed outward by the air pressure during blowing.

[0074] In a cross section perpendicular to the height direction of the inner preform 14 (such as the cross section in FIG. 11D ), the thickness of the inner bag 4 at the thin-walled portion 20a is t1, and the thickness of the inner preform 14 at the thick-walled portion 20b is t2. The minimum value of t1 / t2 is the minimum value obtained by moving the cross section along the height direction of the inner preform 14 and calculating t1 / t2 at each height position. The value of t1 / t2 correlates with T1 / T2, and T1 / T2 can be reduced by reducing t1 / t2. The value of t1 / t2 is preferably 0.1 or greater. This value is, for example, 0.1 to 0.8, specifically, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or 0.8, and may be within a range between any two of the values ​​exemplified here.

[0075] 10, the outer preform 13 is cylindrical with a bottom and includes a mouth portion 13a, a body portion 13b, and a bottom portion 13c. The bottom portion 13c is provided so as to close the lower end of the body portion 13b. The bottom portion 13c is provided with an annular protrusion 13d and a positioning hole (not shown).

[0076] 12, when forming the preform 15, the protrusion 14d is brought into contact with the open end of the mouth portion 13a, and the positioning pin 14c1 is inserted into the positioning hole. This positions the inner preform 14 and the outer preform 13 relative to each other. In this state, the mouth portion 14a faces the mouth portion 13a, and the body portion 14b faces the body portion 13b.

[0077] The mouth portions 13a and 14a become the mouth portion 15a of the preform 15, the body portions 13b and 14b become the body portion 15b of the preform 15, and the bottom portions 13c and 14c become the bottom portion 15c of the preform 15. The body portion 15b and the bottom portion 15c are primarily stretched in the biaxial stretch blow molding. However, since the biaxial stretch blow molding is performed with the annular convex portion 13d supported, the annular convex portion 13d and its inner region are hardly stretched during the biaxial stretch blow molding. The annular convex portion 13d becomes the annular convex portion 3b after molding.

[0078] As shown in FIGS. 11C and 11D , an uneven shape 45 is provided on at least one of the outer surface of the inner preform 14 and the inner surface of the outer preform 13 in a region that will become the shoulder portion 6b of the container body 2 after biaxial stretch blow molding. The uneven shape 45 may be provided in a region that includes the region that will become the shoulder portion 6b, and is preferably provided in a region that includes the region that will become the shoulder portion 6b and the bottom portion 7. Furthermore, the uneven shape 45 is preferably a finer uneven shape than the alternating thickness shape 20. In this embodiment, the uneven shape 45 is formed by an uneven shape 44 provided on the outer surface of the inner preform 14. The uneven shape 44 is preferably provided in a region that includes the mouth portion 14a, the body portion 13b, and the bottom portion 13c. Although no uneven shape is provided on the inner surface of the outer preform 13, an uneven shape may also be provided on the inner surface of the outer preform 13.

[0079] The uneven shape 45 is preferably formed by transferring the uneven shape formed in the mold to the inner preform 14 or the outer preform 13. The uneven shape transferred to the inner preform 14 or the outer preform 13 is an inverse shape of the uneven shape of the mold. The inner preform 14 or the outer preform 13 is preferably formed by injection molding. In this case, the uneven shape of the mold is easily transferred to the inner preform 14 or the outer preform 13 with high accuracy. The uneven shape of the mold is preferably formed by blasting. This makes it possible to form a fine uneven shape in the mold. The uneven shape 45 may also be formed by directly processing the surface of the inner preform 14 or the outer preform 13 (e.g., blasting).

[0080] <Engagement of the Concave and Convex Parts at the Mouth Portion 15a of the Inner Preform 14 and the Outer Preform 13> When the preform 15 is heated and biaxially stretched and blow-molded, the inner surface of the preform 15 (i.e., the inner surface of the inner preform 14) is usually supported. The preform 15 can be conveyed upright, with the bottom 15c facing downward, or inverted, with the bottom 15c facing upward. Upright conveyance is common and preferred. However, conveying the preform 15 upright can cause a problem in that the outer preform 13 becomes detached from the inner preform 14 and falls off. While tightly fitting the outer preform 13 and the inner preform 14 together at the mouth 15a can prevent the outer preform 13 from falling off, this creates a new problem in that the inner bag 4 is difficult to detach from the outer shell 3 in the container body 2 obtained by molding.

[0081] Therefore, in this embodiment, in order to make it possible to easily pull out the inner bag 4 from the outer shell 3 after use while preventing the outer preform 13 from falling off, the inner preform 14 and the outer preform 13 are engaged with each other via a concave-convex structure at the mouth portion 15a.

[0082] In this embodiment, as shown in Fig. 12, the projections 14f provided on the outer peripheral surface of the mouth portion 14a of the inner preform 14 engage with recesses 13f provided on the inner peripheral surface of the mouth portion 13a of the outer preform 13. The projections 14f and recesses 13f correspond to projections 4f and recesses 3f, respectively. The projections 14f are provided with tapered surfaces 14f1, which correspond to 4f1. Therefore, the description of the projections 14f and recesses 13f also applies to the projections 4f and recesses 3f, provided that it does not contradict the spirit of the description, and the description of the projections 4f and recesses 3f also applies to the projections 14f and recesses 13f, provided that it does not contradict the spirit of the description.

[0083] As shown in Fig. 12, when the inner preform 14 is inserted into the outer preform 13, the convex portions 14f are inserted into the outer preform 13 while pushing apart the opening edge of the outer preform 13, and engage with the concave portions 13f. In order to reduce resistance during such engagement, a tapered surface 14f2 is provided on the lower side of the convex portions 14f (the side facing the outer preform 13). On the other hand, no tapered surface is provided on the upper side of the convex portions 14f. Therefore, after the convex portions 14f engage with the concave portions 13f, the engagement is difficult to release.

[0084] Instead of providing the tapered surface 14f2, or in addition to providing the tapered surface 14f1, a tapered surface may be provided on the opening edge of the outer preform 13 to reduce resistance when engaging the convex portion 14f with the concave portion 13f. Furthermore, the concave-convex engagement may be an engagement between a concave portion provided on the outer peripheral surface of the inner preform 14 and a convex portion provided on the inner peripheral surface of the outer preform 13. Furthermore, although the concave portion 13f is configured as a through hole penetrating the outer preform 13, it is sufficient that the concave portion 13f be able to engage with the convex portion 14f, and it is not necessary for the concave portion 13f to penetrate the outer preform 13.

[0085] <Materials and manufacturing method of the inner preform 14 and the outer preform 13> The inner preform 14 and the outer preform 13 can be formed by direct blow molding, injection molding, or the like using thermoplastic resins such as polyester (e.g., PET) or polyolefin (e.g., polypropylene, polyethylene). The inner preform is preferably made of a material with a higher molding shrinkage rate than the outer preform. In this case, a gap is formed between the outer shell 3 and the inner bag 4 due to molding shrinkage, making it easier to introduce outside air into the intermediate space between the outer shell 3 and the inner bag 4.

[0086] In one example, the inner preform 14 is made of polyolefin (e.g., polypropylene), and the outer preform 13 is made of PET. Polyolefin has a larger molding shrinkage rate than PET, so using such a resin configuration makes it easier for a gap to form between the outer shell 3 and the inner bag 4. Furthermore, by making the inner preform 14 and the outer preform 13 from different materials, welding to each other during blow molding is suppressed.

[0087] It is preferable that a laser marking agent be blended into the material that constitutes the inner preform 14. In this case, the laser marking agent is also blended into the inner bag 4 that is formed by molding the inner preform 14.

[0088] Furthermore, if the mouth 14a of the inner preform 14 is made of polyolefin and the mouth 13a of the outer preform 13 is made of amorphous PET, heating the mouth 13a during biaxially stretched blow molding promotes crystallization of the amorphous PET, resulting in a reduction in the dimensions of the mouth 13a. While the mouth 14a is also heated, polyolefin is a crystalline resin, and since it has already crystallized to some extent prior to biaxially stretched blow molding, its dimensional change during biaxially stretched blow molding is smaller than that of amorphous PET. As a result, shrinkage of the mouth 13a becomes more significant than shrinkage of the mouth 14a, resulting in a gap between the protruding portion 14d of the inner preform 14 and the opening edge of the outer preform 13, which may interfere with clamping the preform 15 between a pair of split molds. Furthermore, the container body 2 obtained after molding may have a gap between the protruding portion 4c of the inner bag 4 and the opening edge 3a of the outer shell 3, as shown in FIG. 4A, which may result in a poor appearance. However, in this embodiment, the inner preform 14 and the outer preform 13 are engaged with each other at the mouth portion 15a, and the inner bag 4 and the outer shell 3 are also engaged at the mouth portion 5, thereby preventing the occurrence of the gap.

[0089] The inner preform 14 is preferably formed by direct blow molding. Direct blow molding (blow molding using a molten cylindrical parison) makes it possible to easily form the inner preform 14 having a laminated structure. The outer preform 13 is preferably formed by injection molding.

[0090] After the preform 15 has been biaxially stretched and blow-molded, an outside air introduction hole 16 is formed in the outer shell 3, thereby obtaining the container body 2 shown in FIG.

[0091] Next, a laser marker is used to print information transmission marks 22, 23 on the container body 2. After that, the inner bag 4 is filled with the contents, and then the mouth attachment member 8 is attached to the mouth 5, thereby obtaining the double container 1.

[0092] 2. Other embodiments In the above embodiment, the outside air introduction holes 16 are formed after biaxially stretch blow molding, but through holes that serve as outside air introduction holes may be formed in the outer preform 13 in advance. The air inlet 16 may be formed at the bottom of the outer shell 3 . In the present invention, the structure for twisting the inner bag 4 is not particularly limited, and the inner bag 4 does not have to be configured to rotate in conjunction with the rotation of the opening attachment member 8. In this case, for example, the inner bag 4 may be rotated by pinching it with fingers. Therefore, a cap or pump that does not have a structure for engaging with the inner bag 4 may be used as the opening attachment member 8. Furthermore, the container body 2 does not have to have the protrusion 4c. For example, instead of the protrusion 4c, a flange may be provided at the open end of the inner bag 4, and this flange may be abutted against the open end of the outer shell 3, thereby preventing the inner bag 4 from falling out into the outer shell 3. The uneven shapes 9 and 19, the alternating thickness shapes 10 and 20, the uneven shapes 9 and 19, the annular convex portions 3b and 13d, and the like may be omitted. The inner bag 4 and the outer shell 3, and the inner preform 14 and the outer preform do not need to be engaged with each other by projections and recesses. The container body 2 may be formed by a method other than biaxially stretched blow molding, for example, by direct blow molding in which a laminated parison in a molten state is molded. Information transmission displays 22 and 23 are omitted. [Example]

[0093] 1. Example 1 According to the method described above, the container body 2 (capacity 300 mL) shown in FIG. 1 was produced by biaxially stretching and blow-molding the preform 15 shown in FIGS. 10 to 13 . The inner preform 14 was produced by injection molding a propylene-ethylene random copolymer (type: Wintec, manufactured by Japan Polypropylene Corporation). The outer preform 13 was produced by injection molding PET (type: titanium catalyst grade, manufactured by Teijin Limited) at 300°C to form the outer preform shape, followed by rapid cooling to 20°C. The molten PET was converted to an amorphous state by rapid cooling. The mold for forming the inner preform 14 was subjected to abrasive blasting on the surface corresponding to the outer surface of the inner preform 14, forming an irregular shape. The blasting was performed using white alumina #80 (WA#80).

[0094] Such a preform 15 was heated to 110° C. (the temperature at the center in the longitudinal direction of the preform 15) and then subjected to biaxial stretch blow molding to obtain a container body 2.

[0095] A test piece (10 mm x 75 mm) in which the inner bag 4 and outer shell 3 overlapped was cut out from the obtained container body 2, and this test piece was set in a friction coefficient measuring device (model: HEIDON-10, Shinto Scientific Co., Ltd.). More specifically, the inner bag 4 was fixed to a lifting plate, and a 150 g flat indenter was attached to the outer shell 3. Next, the lifting plate was tilted, and the angle at which the outer shell 3 began to slide relative to the inner bag 4 was measured. The average angle obtained by measuring three samples was 18.8 degrees.

[0096] 2. Comparative Example 1 The angle at which the outer shell 3 began to slide relative to the inner bag 4 was measured in the same manner as in Example 1, except that the mold used to form the inner preform 14 had a mirror-polished surface corresponding to the outer surface of the inner preform 14. In all three samples, the outer shell 3 did not slide relative to the inner bag 4, even at 57.5 degrees, the measurement limit of the device.

[0097] 3. Notes The original claims of the original application are attached. [1] A double container having a container body with an inner bag and an outer shell, the container body having a mouth, a body, and a bottom, the mouth being a tubular portion with an open end, the body being positioned adjacent to the mouth on a side farther from the open end than the mouth and having a larger outer diameter than the mouth, the bottom being configured to close the lower end of the body, the body having a shoulder whose outer diameter increases with increasing distance from the mouth, and at least one of the outer surface of the inner bag and the inner surface of the outer shell at the shoulder of the container body is provided with an uneven shape that reduces the contact area between the outer surface of the inner bag and the inner surface of the outer shell. [2] A double container as described in [1], wherein when the uneven shape is a first uneven shape, the other of the outer surface of the inner bag and the inner surface of the outer shell either does not have an uneven shape or has a second uneven shape that is not complementary to the first uneven shape. [3] A method for manufacturing a double container, comprising a step of manufacturing a container body by biaxially stretching blow molding a preform consisting of an inner preform and an outer preform, wherein an uneven shape is provided on at least one of the outer surface of the inner preform and the inner surface of the outer preform in a region that will become the shoulder of the container body after the biaxially stretching blow molding. [4] The method according to [3], wherein the uneven shape is provided on the outer surface of the inner preform. [5] A method according to [3] or [4], wherein the uneven shape is formed by transferring an uneven shape formed on a mold by blasting to the inner preform or the outer preform. [Explanation of symbols]

[0098] 1:Double container 2: Container body 3: Outer shell 3a: Open end 3b: Annular convex part 3c: Through hole 3f: Recess 4: Inner bag 4c:Protrusion 4c1:Protruding tube 4c2: Engagement protrusion 4c3: Engagement flange 4c4: Abutting flange 4c5: Circumferential slope 4d: side 4e: Protrusion 4f: Convex part 4f1: Tapered surface 5: Mouth 5a: Engagement part 5a1: Male thread 5b: Flange 5c: Open end 6: Body 6b:Shoulder 6c: Body 6d: Recess 6e: Groove 7: Bottom 7a: Bottom concave area 7a1: Peripheral surface 7a2: Bottom 7b: Peripheral area 8: Mouth attachment member 8a: Outer cylinder 8b: Intermediate cylinder 8c: Inner cylinder 8d: Engagement part 8d1: Female thread 8e: Claw part 8e1:Top surface 8e2: Lower slope 8f: Top board 8g: Nozzle 8h: Through hole 9: Uneven shape 9a: Concave 9b: Convex strip 10: Alternating thickness shape 10a: Thin section 10b: Thick wall part 11: Groove 13: Outer preform 13a: Mouth 13b: Torso 13c: Bottom 13d: Annular convex part 13f: Recess 14: Inner preform 14a: Mouth 14b: Torso 14c: Bottom 14c1: Locating pin 14d:Protrusion 14f: Convex part 14f1: Tapered surface 14f2: Tapered surface 15: Preform 15a: Mouth 15b: Body 15c: bottom 16: Outside air intake 19: Uneven shape 20: Alternating thickness shape 20a: Thin section 20b: Thick wall part 21: Groove 22: Information transmission display 22a:Recycle mark 22b: Message 23: Information transmission display 23a:Recycle mark 23b: Message 33: Uneven shape 33a: Convex part 33b: recess 34: Uneven shape 34a: Convex part 34b: recess 35: Uneven shape 44: Uneven shape 45: Uneven shape

Claims

1. A method for manufacturing a double container, comprising a step of manufacturing a container body by biaxially stretching blow molding a preform composed of an inner preform and an outer preform, a first uneven shape is provided on at least one of the outer surface of the inner preform and the inner surface of the outer preform in a region that will become a shoulder portion of the container body after the biaxially stretched blow molding.

2. 10. The method of claim 1, The method, wherein the first texture is provided on an outer surface of the inner preform.

3. 3. The method of claim 1 or claim 2, The method, wherein the first irregularity is not provided on an inner surface of the outer preform.

4. The method according to any one of claims 1 to 3, The method, wherein the first uneven shape is formed by transferring an uneven shape formed on a mold by blasting to the inner preform or the outer preform.

5. The method according to any one of claims 1 to 4, The double container has a container body having an inner bag and an outer shell, the container body includes a mouth, a body, and a bottom, the mouth being a cylindrical portion having an open end, the body being disposed adjacent to the mouth on a side farther from the open end than the mouth, and having a larger outer diameter than the mouth, and the bottom being configured to close the lower end of the body, The body portion has a shoulder portion whose outer diameter increases with increasing distance from the mouth portion, a second uneven shape is provided on at least one of the outer surface of the inner bag and the inner surface of the outer shell at the shoulder portion of the container body, the second uneven shape reducing the contact area between the outer surface of the inner bag and the inner surface of the outer shell; The method, wherein the outer surface of the inner bag and the inner surface of the outer shell are in contact with each other at the convex portions of the second uneven shape, but are not in contact with each other at the concave portions of the second uneven shape.

6. The method according to any one of claims 1 to 5, The double container has a container body having an inner bag and an outer shell, the container body includes a mouth, a body, and a bottom, the mouth being a cylindrical portion having an open end, the body being disposed adjacent to the mouth on a side farther from the open end than the mouth, and having a larger outer diameter than the mouth, and the bottom being configured to close the lower end of the body, The body portion has a shoulder portion whose outer diameter increases with increasing distance from the mouth portion, a second uneven shape is provided on at least one of the outer surface of the inner bag and the inner surface of the outer shell at the shoulder portion of the container body, the second uneven shape reducing the contact area between the outer surface of the inner bag and the inner surface of the outer shell; The method, wherein the second uneven shape has recesses and protrusions arranged irregularly.

7. 7. The method of claim 5 or claim 6, The second texture is provided on the outer surface of the inner bag.

8. The method according to any one of claims 5 to 7, The method, wherein the second texture is not provided on an inner surface of the outer shell.

9. The method according to any one of claims 5 to 8, a ratio of the depth of the recessed portion as viewed from the highest portion of the protruding portion of the second uneven shape to the thickness of the inner bag at the highest portion of the protruding portion is 0.01 to 0.5.

Images